1. Field of the Invention
The present invention relates to a stereo video data coding apparatus, or in particular, to a stereo video data coding apparatus for transmitting a motion vector and a predictive error of the stereo video data subjected to motion compensation through one channel and transmitting a motion vector, a parallax vector and a predictive error of the stereo video data subjected to motion compensation and parallax compensation through the other channel.
2. Description of the Related Art
An example of a conventional stereo video data coding apparatus will be explained with reference to the block diagram of FIG. 5. The stereo video data coding apparatus comprises two coders for coding video data of left and right channels.
The coder for the left channel (or the basic channel) includes an original picture frame memory 11 for storing the original image, a subtractor 12 for generating a predictive error signal, an orthogonal transformer 13 for performing orthogonal transformation such as DCT transformation of the predictive error signal output from the subtractor 12, a quantizer 14 for quantizing the data subjected to orthogonal transformation, and a variable length coder 15 for subjecting the quantized data to variable length coding. The coder further includes an inverse quantizer 16 for inversely quantizing the data quantized by the quantizer 14, an inverse orthogonal transformer 17, an adder 18, a reproduced picture frame memory 19 for temporarily storing a reproduced picture, a motion compensator 20 for performing motion compensation with the original picture from the original picture frame memory 11 and the reproduced picture, and a predictive picture frame memory 21.
The coder for the right channel (or the extended channel), on the other hand, includes component parts 31 to 40 and 42 similar to the coder for the left channel described above, except for a predictive mode selector 41 and a parallax compensator 43. The reproduced picture from the reproduced picture frame memory 19 is applied to the parallax compensator 43.
In this configuration, the left channel is coded based on the normal motion compensation and DCT. The right channel, on the other hand, is coded based on motion compensation or parallax compensation and DCT. Specifically, the prediction mode selector 41 selects the motion compensator 40 and the parallax compensator 43, whichever is lower in predictive error, and connects to the predictive picture frame memory 42. Other operations are similar to those for the left channel.
In the prior art described, however, the motion compensator 40 for the right channel has a configuration of the same size as the motion compensator 20 for the left channel, thereby posing the problem of the magnitude of the circuit size. The motion vector search of a particular macroblock, for example, is conducted in the range of xc2x1128 pixels by xc2x132 lines. For realizing this with a LSI for motion detection which covers the range of xc2x18 pixels by xc2x18 lines, for example, 64 LSI chips are required.
The object of the present invention is to provide a stereo video data motion vector coding apparatus which obviates the problems of the prior art described above and can detect motion vectors with small circuit size and high accuracy.
The first aspect of the invention lies in that a stereo video data coding apparatus comprises means for determining a macroblock on the basic channel corresponding to each macroblock constituting a unit of motion vector detection of the extended channel from the parallax vector between the two channels and acquiring a motion vector of said corresponding macroblock and means for determining the detection area of the motion vector of the macroblock constituting a unit of motion vector detection of said extended channel based on said acquired motion vector.
The second aspect of the invention lies in that a stereo video data coding apparatus comprises means for acquiring a motion vector of an adjacent macroblock for each macroblock constituting a unit of motion vector detection of the extended channel.
The third aspect of the invention lies in that a stereo video data coding apparatus comprises means for evaluating the utility of said acquired motion vectors and means for determining the detection area of the motion vector of the macroblock constituting a unit of motion vector detection of said extended channel based on a motion vector high in utility evaluation.
The fourth aspect of the invention lies in that the range of motion vector detection of a macroblock constituting a unit of motion vector detection of the extended channel is limited to the acquired motion vector described above, motion vectors high in evaluation or motion vectors in the neighborhood thereof.
According to the first to third aspects described above, a highly accurate motion vector can be used as a reference for determining the motion vector detection range of the macroblock of the extended channel. As a result, the range of motion vector detection can be reduced remarkably as compared with the prior art. Also, according to the fourth aspect, the motion vector detection range can be reduced to a very small area of xc2x18 pixels by xc2x18 lines, for example, around the macroblock corresponding to the acquired motion vector or the motion vector high in evaluation.